Temperature dependence of thermal expansion of ceramics and metals for electronic packages

The X-Y (in-plane) expansivity was measured over the -40-140°C range for several of the ceramics used in modern hybrids, single-chip packages, and multichip modules. These thermal expansion data were compared to those of silicon and the materials used for leads, lids, heat spreaders, and sinks. The expansivity of aluminas of different purities (92-99.5%), low-temperature cofired ceramics, aluminum nitride, and beryllia was measured. A k=4.8 sample was expansivity-matched to Si, and a k=8.0 sample matched to alumina. No significant effect of metallization of the multilayers on the expansivity was found. Aluminum nitride was found to be well matched to silicon, whereas beryllia was found to be well matched to alumina, Kovar, Invar, Alloy 42, molybdenum, and two composites, namely copper-molybdenum-copper and copper-Invar-copper, were measured. Kovar is well matched to alumina ceramic at room temperature; below and above room temperature, however, the expansivity of Kovar diverges from that of alumina